In recent years, when an electrophotographic process is applied to form images, downsizing of toner particles is promoted in order to attain higher image quality, and a polymerized toner is manufactured to meet this demand. This polymerized toner is composed of resin particles prepared by conducting a polymerization process via emulsion polymerization and the like, colorant particles, and toner particles acquired by coagulating other particles as a toner composition if desired.
After oil droplets are formed by dispersing a polymerizable monomer raw material in an aqueous medium, used subsequently to incorporate an emulsifier, the resin particles to acquire a polymerized toner were conventionally prepared via emulsion polymerization in which radical polymerization was conducted via oil droplets by adding a polymerization initiator. A styrene-acryl based resin particles exemplified, for example (refer to Patent Document 1 and Patent Document 2, for example).
Since kinds of polymerizable monomers used for radical polymerization are limited in such a toner manufacturing method, the resulting toner is limited to toner particles composed of vinyl based resin particles or acryl based resin particles.
Since in the case of polyester resin, a toner exhibits excellent fixability obtained by excellent viscoelasticity of the polyester resin, a toner composed of toner particles containing coagulated polyester resin particles is desired. In order to acquire a toner containing such polyester resin particles, a solution in which the polyester resin is dissolved in an organic solvent is dispersed in an aqueous medium, and these polyester resin particle-to-polyester resin particles are subsequently coagulated with colorant particles, whereby toner particles can be prepared via solvent removal. This toner manufacturing method is exemplified (refer to Patent Document 3, for example).
Since polyester resin which was dissolved in an organic solvent could only be used in a limited way in the case of such a manufacturing method, it was, however, difficult to produce a toner composed of toner particles of polyester resin having a cross-linking structure in which the high temperature off-setting phenomenon during the fixing process could be largely eliminated via this viscoelasticity. Bothersome processes such as the process to remove organic solvents and so forth, in the above-cited method, also have to be conducted, and these processes may cause problems such that the organic solvent has remained.
(Patent Document 1) Japanese Patent O.P.I. Publication 2000-214629
(Patent Document 2) Japanese Patent O.P.I. Publication 2001-125313
(Patent Document 3) Japanese Patent O.P.I. Publication 2004-109848